1. Field of the Invention
The present invention relates to a discontinuous reception method for a mobile communication terminal device and a mobile communication terminal device and, more particularly, to processing to select a discontinuous reception period.
2. Description of the Related Art
In mobile communication systems using cellular systems such as the CDMA (Code Division Multiple Access) system, the mobile communication service area is divided into small-scale regions known as cells and one or a plurality of base stations are installed in each cell. Further, a mobile station (mobile communication terminal device) is positioned in a certain cell and, during standby (Idle Mode), selects and renders a base station that is installed in this cell as the standby base station (Serving Cell) and establishes a wireless communication link with the standby base station.
Further, the mobile station performs discontinuous reception, waking up discontinuously in each discontinuous reception cycle, receiving system paging information which could be related to an incoming call that is sent by the standby base station and detecting the existence of an incoming call to the mobile station's own station. Further, when there is an incoming call to the mobile station's own station, the mobile station establishes the required channel with the standby base station and performs communications via the established channel. Here, the discontinuous reception cycle is established to fulfill the contrary objectives of reducing the amount of electrical power consumed by the mobile station and of shortening the time required to complete the establishment of a channel in the event of an incoming call (See “W-CDMA Mobile Communication Systems” by Keiji Tachikawa (Ed.); Manuzen Co. Ltd, Jun. 25, 2001, pages 222 to 223, for example).
Meanwhile, a telephone call of the Push-to-Talk (referred to as ‘PTT’ hereinafter) system in which a user performs a predetermined operation to request the floor in order to make a call and only one mobile station that has obtained the floor can transmit a speech signal and the other one or plurality of mobile. That is to say, to establish a PTT-system telephone call, a certain mobile station needs to request the establishment of a PTT session to connect to the other one or plurality of mobile stations at first, then request the occupation of the floor to speak. A mobile station can invite other online mobile stations to join a PTT session onward by itself, or it can join a PTT session owned by other mobile station by answering to the PTT mobile terminated call from the owner of the session.
That is, when a certain mobile station has requested the establishment of a PTT session, information relating to an incoming call is transmitted by the mobile station to the mobile station that requested participation in the session and, when a certain mobile station that is a member of a certain PTT session has requested the floor, information relating to the incoming call is transmitted to a mobile station that is a member of the PTT session with the exception of this mobile station.
Because the processing for the registration of the mobile station participating in the session takes time, there is no need to focus on the time required until completion of the establishment of a channel in the establishment of a PTT session. Therefore, the discontinuous reception cycle when the mobile station is not a member of the PTT session is suitably set relatively long with a focus on reducing amount of electrical power consumed by the mobile station.
On the other hand, when a certain mobile station requests the floor, the mobile station obtains the floor in an instant and the transmission of the speech signal must be at the start of a telephone call with a short wait time. The discontinuous reception cycle in a case where the mobile station is a member of the PTT session is suitably set relatively short with a focus on shortening the time required to complete the establishment of the channel.
However, the method disclosed in “W-CDMA Mobile Communication Systems” by Keiji Tachikawa (Ed.); Maruzen Co. Ltd, Jun. 25, 2001, pages 222 to 223 mentioned earlier has been faced by the problem of not being able to change the discontinuous reception cycle.